The present invention relates to a winding spindle for use on a yarn take-up machine, and of the type which is adapted to coaxially mount a yarn winding bobbin. More particularly, the invention relates to a winding spindle of the described type and wherein the winding bobbin can be clamped on the spindle by applying radial forces, the radial forces being applied by clamping members.
A winding spindle of the described type is known, for example, from DE-OS 24 57 821. In this known winding spindle, the winding bobbin is inserted with its one end over a supporting surface and clamped in place in the region of the other end by a radially widening, elastic ring. To this end, the elastic ring is biased by a compression spring, and is thereby axially compressed. This axial compression results in an increase in diameter and a radial clamping force being exerted on the winding bobbin.
The above construction permits radial forces to be applied to the winding bobbin only to a limited extent, since the change in diameter of the elastic ring is limited. Among other things, this limitation results from the fact that when the radial enlargement of the elastic ring becomes too great, the running position of the winding bobbin could diverge from the axially concentric position, thereby causing problems of imbalance.
Another problem is that the enlargement of the diameter is dependent on the force of the associated spring. In general, stronger springs allow the elastic rings to be compressed to a greater extent, thereby improving the attainable enlargement of diameter. However, the mass of the winding spindle increases as a result of this construction, which is not desirable in view of the high spindle speeds usual at present.
It is known from EPO Patent 270 826 B1 that the elastic ring can be widened by a cone arranged in its inside diameter, and where the cone is biased by axial spring forces. To release the tension, the axially directed compression spring is compressed such that the cone is moved from the inside diameter of the elastic ring in the direction of the smaller cone diameter. In so doing, the elastic ring relaxes and releases the winding bobbin.
The above system needs to overcome very high frictional forces, since the axial movement of the cone generates, while the elastic ring widens, an increasing surface pressure between the cone and the elastic ring. Therefore, it is necessary that the compression springs be able to apply adequately high compressive forces, in particular during the decisive clamping phase of the pertinent elastic ring, which necessitates a correspondingly strong compression spring and a correspondingly high bias.
It is accordingly an object of the present invention to provide a winding spindle which, while being of the lightest possible construction, is able to apply with little damage to the winding bobbins the highest possible clamping forces.